It is known that in motor vehicles, electromechanical adjusting drives are employed to adjust window panes, sliding roofs or other actuating parts, for which anti-trap protection can be legally prescribed on safety grounds. This anti-trap protection prevents bodily injury being incurred as a result of impermissibly high pinching forces in the case of manually triggered, but autonomously running closure.
The anti-trap protection can, however, only be effective if the position of the actuating part assumed by the controller tallies with the actual position. In order to ensure this is the case, an initialization of the adjusting drive is required, which can first be performed during manufacture of the drive but also during operation, and during which a reference position is determined. In the case of an automobile window lifter, the window pane is generally moved upwards, against a rubber seal in the door frame. The blockage position in the closed position of the pane is regarded as a reference point (“absolute zero”) for all subsequent adjusting movements of the window pane.
Errors may, however, occur during initialization. If during the initialization run, the window pane or the sliding roof are inadvertently blocked, for example by an obstacle in the adjustment path, or a mechanical stiffness arises in the transmission system, or a temporary fault occurs with the metrological recording of the blockage status, then the defined reference position is incorrect, that is to say it does not tally with the actual end position. Such a fault could be detected during the manufacturing process in the course of quality assurance, for example by means of a visual check as to whether the window pane is actually in an open or closed position. If this is not the case, the initialization must be performed afresh. This is associated with a corresponding degree of effort. If, however, this fault occurs during operation in the case of proper usage, the customer must seek a specialist workshop, with the associated effort.
If an initialization fault of this kind remains undetected, this has the further consequence that all adjusting movements subsequent to the initialization phase are based on a false reference point. This also has the consequence that in the case of a window lifter, the anti-trap protection no longer acts in safety-critical proximity to the door frame, but is shifted to an area at some distance from this. However in the case of the automatically running closure of the window pane, the closing force is thus no longer limited in the legally prescribed region of the adjustment path. Bodily injuries may be suffered as a result.